What’s Vulnerable › Vulnerabilities

CVE-2026-39838: ProofreadPage improperly sanitizes multiline styles using Sanitizer::checkCSS

• Severity: medium (CVSS 6.9 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-07 · updated 2026-07-21
• Weakness: CWE-79

Description

Improper neutralization of input during web page generation ('cross-site scripting') vulnerability in Wikimedia Foundation MediaWiki - ProofreadPage Extension allows XSS Targeting Non-Script Elements. The issue has been remediated on the `master` branch, and in the release branches for MediaWiki versions 1.43, 1.44, and 1.45.

Affected products

• Wikimedia Foundation MediaWiki - ProofreadPage Extension: before 1.43 — fixed in 1.43

How to fix

Upgrade to a fixed version: Wikimedia Foundation MediaWiki - ProofreadPage Extension 1.43. Check the vendor advisory for mitigations.

References

• https://gerrit.wikimedia.org/r/q/Idd51e18479b32b7176b43ff74ca1c49d6bdd0628
• https://phabricator.wikimedia.org/T406088

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